The present application claims priority to and benefit of Japanese Patent Application No. 2014-118556 filed on Jun. 9, 2014, Japanese Patent Application No. 2014-131045 filed on Jun. 26, 2014, and Japanese Patent Application No. 2015-049038 filed on Mar. 12, 2015, the contents of which are incorporated by reference herein in their entirety.
A CMP (Chemical Mechanical Polishing) device has a polishing device for polishing a surface of a semiconductor substrate on which a semiconductor chip is formed and a cleaning device for cleaning the semiconductor substrate polished by the polishing device while supplying a cleaning chemical. This cleaning device creates a cleaning chemical (diluted chemical) by mixing dilution water such as DIW (De-Ionized Water) in a chemical and cleans the semiconductor substrate by using the cleaning chemical (see Japanese Patent Laid-Open No. 2009-54959, for example).
In the cleaning device using the cleaning chemical, a cleaning chemical supplying device having an in-line flow meter in which a chemical flow meter and a DIW flow meter are juxtaposed in a pair has been used. Each of the chemical flow meter and the DIW flow meter includes a CLC (Closed Loop Controller) and executes feedback control of the respective flow rates so that a chemical flow rate and a DIW flow rate form a certain ratio. As a result, the chemical diluted at a certain ratio is supplied to a cleaning tank of the cleaning device.
In the prior-art chemical supplying device, the chemical flow meter, the DIW flow meter, and an in-line mixer for mixing the chemical and the DIW whose flow rates are controlled are accommodated in one box. That is, one DIW flow meter is designed to be combined with one chemical flow meter, and a size of one box is designed to contain only the two flow meters.
In recent years, in the cleaning device provided in the CMP device, a process for cleaning the semiconductor substrate by alternately using an acid chemical and an alkaline chemical is in demand. As described above, since the prior-art cleaning device is designed with the size that the box can contain only two flow meters, only two types of chemical flow meters can be contained in the box, and the DIW flow meter cannot be additionally provided in the box. Thus, in the prior-art chemical supplying device, two flow meters for chemicals are arranged in the box and two types of cleaning chemicals diluted in advance are supplied through the respective flow meters.
However, in the chemical supplying device using two types of cleaning chemicals diluted in advance, if a dilution ratio of the cleaning chemical is changed with a change of a process recipe, a cleaning chemical with a different dilution ratio needs to be prepared. That is, this chemical supplying device cannot flexibly handle the change of the process recipe.
On the other hand, if the above-described in-line flow meter is used, the change of the dilution ratio with the change of the process recipe can be handled only by changing flow rate set values of the chemical flow meter and the DIW flow meter. However, in order to supply two types of chemicals to the cleaning device, two in-line flow meters need to be prepared. In this case, since the DIW flow meter is provided in each of the two in-line flow meters, it has a problem in that the size of the chemical supplying device increases.
A differential pressure flow meter (orifice flow meter) is used in general for the chemical flow meter and the DIW flow meter. The differential pressure flow meter has an orifice arranged on a path through which a fluid passes and measures a mass flow rate (flow velocity) of the fluid on the basis of a differential pressure. A measurement range of the differential pressure flow meter, that is, a flow rate range controllable by the CLC is determined by a diameter of the orifice in terms of its structure. That is, the measurement range of the orifice flow meter is set in general such that a maximum/minimum flow rate ratio is approximately 1:9 as from 30 ml/min to 300 ml/min, for example. Therefore, the flow rate range controllable by the chemical flow meter and the DIW flow meter becomes a range determined in advance in terms of its structure.
In the prior-art cleaning chemical supplying device, if the dilution ratio of the cleaning chemical is changed or a supply flow rate of the cleaning chemical is changed with the change of the process recipe, required flow rates of the chemical and the DIW might deviate from the flow rate range controllable by the currently selected chemical flow meter and DIW flow meter in some cases. In such a case, the change of the process recipe is handled by selecting the chemical flow meter and the DIW flow meter again and by replacing the flow meters with those in the controllable flow rate range. Thus, if the flow rates of the chemical and the DIW required for the changed process recipe deviate from the flow rate ranges of the chemical flow meter and the DIW flow meter, the chemical flow meter and the DIW flow meter need to be replaced at each change of the process recipe, which takes a labor.
In the cleaning device of the CMP device, the cleaning chemical is used not only for cleaning of the substrate but also for prevention of oxidation of the substrate for the substrates waiting for cleaning (substrate to be cleaned next). In a cleaning process of the prior-art CMP device, cleaning of the substrate is not performed at the same time as waiting for cleaning. That is, while the substrate is being cleaned, the substrate is not transferred to a standby spot. However, in order to improve a throughput of the cleaning process, a process in which cleaning of the substrate and waiting for cleaning are performed at the same time is in demand in recent years. If cleaning of the substrate and waiting for cleaning are performed at the same time, since the cleaning chemical is used for each of them, larger flow rates of the chemical and the DIW than before become necessary. Moreover, a process capable of supplying small flow rates of the chemical and the DIW also needs to be handled. The flow rate range controllable by the prior-art chemical flow meter and the DIW flow meter cannot handle various processes.
The present invention was made in order to solve at least one of the above-described problems and one of its objects is to provide a cleaning chemical supplying device and a cleaning chemical supplying method which can flexibly handle a change in a dilution ratio and can suppress an increase in a device size.
Another object of the present invention is to supply a chemical and DIW in a wide flow rate range without replacing the flow meter.